The Annoyance Filter.pdf - Fourmilab

§191 ANNOYANCE-FILTER CLASSIFY MESSAGE 161
191. If we’re producing a message transcript, just before writing it add the annotations to the end of
the header which indicate the junk probability and classification of the message based on the threshold
settings. After these, other annotations requested by the −−annotate option are appended.
The test for the end of the message header where we insert the annotations is a little curious. When
we’re processing a message received from a POP3Proxy server, the transcript will contain the CR from
the CR/LF termination sequences as required by POP3. (The final line feed will have been stripped by
getline as the message was read.) Preserving these terminators allows us to use the standard mechanisms
of mailFolder without lots of special flags, so we deem a line the end of the header if it’s either zero
length (read from a UNIX mail folder with getline or if it contains a single CR (received from a POP3
server). In the latter case, we set transEndl so as terminate annotations we add to the transcript with
CR/LF as well.
〈 Add annotation to message transcript 191 〉 ≡
ostringstream os ;
list〈string〉::iterator p;
string transEndl = ""; /∗ Find the end of the header in the message. If this fails simply append
the annotations to the end of the message. ∗/
for (p = messageTranscript .begin ( ); p ≠ messageTranscript .end ( ); p++) {
if (p ⃗ length ( ) ≡ 0) {
break;
}
if (∗p ≡ "\r") {
transEndl = "\r";
break;
}
}
double jp = junkProb; /∗ If the probability is sufficiently small it to be edited in scientific
notation, force it to zero so it’s easier to parse. ∗/
if (jp < 0.001) {
jp = 0;
}
os ≪ Xfile ≪ "−Junk−Probability:␣" ≪ setprecision (3) ≪ jp ≪ transEndl ;
messageTranscript .insert (p, os .str ( ));
os .str ("");
os ≪ Xfile ≪ "−Classification:␣";
if (junkProb ≥ junkThreshold ) {
os ≪ "Junk";
}
else if (junkProb ≤ mailThreshold ) {
os ≪ "Mail";
}
else {
os ≪ "Indeterminate";
}
os ≪ transEndl ;
messageTranscript .insert (p, os .str ( ));
if (Annotate (’w’)) {
addSignificantWordDiagnostics (messageTranscript , p, rtokens , transEndl );
}
if (Annotate (’p’) ∨ Annotate (’d’)) {
while (¬parserDiagnostics .empty ( )) {
ostringstream os ;